java - Jackson Convert Object to Map preserving Date type

Question

I am using Jackson ObjectMapper to convert a Java Bean to a Map.

However, it is not preserving the Date object, rather it gets converted to Long.

Here is the failing test case,

@Test
public void testObjectToMapDate() {

    User user = new User();
    user.setDob(new Date());

    ObjectMapper mapper = new ObjectMapper();
    Map<String, Object> map = mapper.convertValue(user, Map.class);
    assertTrue(map.get("dob") instanceof Date);

}

Is there a simple solution to this?

Answer 1

Jackson, by default, serializes java.util.Date instances as numeric timestamps. You can configure Jackson to use a textual representation with

mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false); // it's true by default

or provide your own JsonSerializer.

However, when you are doing the conversion, there is absolutely nothing in the intermediate JSON and in the target type, Map, to indicate to Jackson that it should deserialize it as a Date object. Without extra type information, Jackson will always deserialize it using its defaults (long, double, String, LinkedHashMap).